The present invention relates to rotating electrical machines such as high speed starter generators for gas turbine engines and, more particularly, to a terminal assembly used to transmit electrical energy between starter generators and external systems and equipment, and a method of assembling and installing the terminal assembly in the starter generator.
An aircraft may include various types of rotating electrical machines such as, for example, generators, motors, and motor/generators. Motor/generators are used as starter-generators in some aircraft, since this type of rotating electrical machine may be operated as either a motor or a generator.
An aircraft starter-generator may include three separate brushless generators, namely, a permanent magnet generator (PMG), an exciter motor/generator, and a main motor/generator. The PMG includes permanent magnets on its rotor. When the PMG rotates, AC currents are induced in stator windings of the PMG. These AC currents are typically fed to a regulator or a control device, which in turn outputs a DC current if operating as a generator, or an AC current if operating as a motor.
If the starter-generator is operating as a generator, the DC current from the control device is supplied to stator windings of the exciter. As the rotor of the exciter rotates, three phases of AC current are typically induced in the rotor windings. Rectifier circuits that rotate with the rotor of the exciter rectify this three-phase AC current, and the resulting DC current is provided to the rotor windings of the main motor/generator. Finally, as the rotor of the main motor/generator rotates, three phases of AC current are typically induced in its stator, and this three-phase AC output can then be provided to a load such as, for example, an aircraft electrical system.
If the starter-generator is operating as a motor, the AC current form the control device is supplied to both the stator of the main motor/generator and the stator of the exciter. This AC current induces a rotating magnetic field in the main motor/generator and exciter stators, which causes the rotor to rotate and supply mechanical output power.
The electrical power output from, or supplied to, the starter-generator may be supplied from or to stator output leads, via one or more terminal assemblies. The terminal assemblies may consist of feedthroughs that extend through the generator housing, and are coupled to the stator output leads within the generator housing and to a terminal block assembly outside of the generator housing. Insulators may be used with the feedthroughs to electrically insulate the feedthroughs from the housing. When used in oil-cooled generators, seals may additionally be used to provide a sufficiently leak-tight seal around the feedthroughs.
In some cases, the feedthroughs are coupled to the stator output leads and the terminal block assembly by a relatively high temperature brazing process. During this process, the insulators and seals may be protected with one or more heat sinks to reduce the likelihood of component degradation and/or failure from exposure to the heat. Thus, some feedthroughs are relatively large in size in order to allow an effective connection to a heat sink during the brazing process. Even with heat sinks installed during the brazing process, the insulators and seals are still damaged in some instances and are replaced. Moreover, after the feedthroughs are installed, various testing may still have to be performed to verify proper electrical and mechanical performance, which can increase costs. In addition, repairing feedthroughs installed in this manner can be time consuming and complex, thereby increasing repair costs.
Hence, there is a need for a terminal assembly that addresses one or more of the above-noted drawbacks. Namely, a terminal assembly and installation method that does not result in significant component damage or failure during installation, and/or does not require significant amounts of verification testing after installation, and/or allows for comparatively easy and less time consuming repairs, and is therefore less costly as compared to present assemblies. The present invention addresses one or more of these needs.
The present invention provides a terminal assembly for electrical machines, such as high speed aircraft starter-generators, that does not result in significant component damage or failure during installation, is relatively simple in design, is relatively inexpensive, and is relatively easy to install.
In one embodiment of the present invention, and by way of example only, a starter-generator for a gas turbine engine includes a housing, a stator, a rotor, and a terminal assembly. The stator is mounted within the housing, and the rotor is rotationally mounted within the stator. The terminal assembly is mounted on the housing and includes a feedthrough body, at least one electrically conductive electrode, and a hermetic seal. The feedthrough body has an outer surface and an opening therethrough forming an inner surface. Each electrically conductive electrode extends through the opening in the feedthrough body, and the hermetic seal coupes the electrode to the feedthrough body inner surface.
In yet another exemplary embodiment, a terminal assembly for electrically connecting a stator mounted within the housing of an electrical machine to external equipment and systems includes a terminal housing, a feedthrough body, at least one electrically conductive electrode, and a hermetic seal. The terminal housing is adapted for coupling to the machine housing. The feedthrough body has an outer surface and an opening therethrough forming an inner surface. Each electrically conductive electrode extends through the opening in the feedthrough body, and the hermetic seal coupes the electrode to the feedthrough body inner surface.
In still another exemplary embodiment, an electrical feedthrough assembly for electrically connecting a stator housed within an electrical machine to external systems and equipment includes a feedthrough body, at least one electrically conductive electrode, and a hermetic seal. The terminal housing is adapted for coupling to the machine housing. The feedthrough body has an outer surface and an opening therethrough forming an inner surface. Each electrically conductive electrode extends through the opening in the feedthrough body, and the hermetic seal coupes the electrode to the feedthrough body inner surface.
In yet still another exemplary embodiment, a method of assembling a terminal assembly for a rotating electrical machine housing includes providing a feedthrough body having an outer surface and an opening therethrough forming an inner surface, inserting at least one electrically conductive electrode into the feedthrough body and through the opening therein, and coupling the electrode to the feedthrough body inner surface with a hermetic seal.
Other independent features and advantages of the preferred terminal assembly and method will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.